docs: def mac_set_relative_dylib_deps(libname):
      """
      On Mac OS X set relative paths to dynamic library dependencies of `libname`.
  
      Relative paths allow to avoid using environment variable DYLD_LIBRARY_PATH.
      There are known some issues with DYLD_LIBRARY_PATH. Relative paths is
      more flexible mechanism.
  
      Current location of dependend libraries is derived from the location
      of the executable (paths start with '@executable_path').
  
      @executable_path or @loader_path fail in some situations
      (@loader_path - qt4 plugins, @executable_path -
      Python built-in hashlib module).
      """
  
      from PyInstaller.lib.macholib import util
      from PyInstaller.lib.macholib.MachO import MachO
  
      # Ignore bootloader otherwise PyInstaller fails with exception like
      # 'ValueError: total_size > low_offset (288 > 0)'
      if os.path.basename(libname) in _BOOTLOADER_FNAMES:
          return
  
      def match_func(pth):
          """For system libraries is still used absolute path. It is unchanged."""
          # Match non system dynamic libraries.
          if not util.in_system_path(pth):
              # Use relative path to dependend dynamic libraries bases on
              # location of the executable.
              return os.path.join('@executable_path', os.path.basename(pth))
  
      # Rewrite mach headers with @executable_path.
      dll = MachO(libname)
      dll.rewriteLoadCommands(match_func)
  
      # Write changes into file.
      # Write code is based on macholib example.
      try:
          f = open(dll.filename, 'rb+')
          for header in dll.headers:
              f.seek(0)
              dll.write(f)
          f.seek(0, 2)
          f.flush()
          f.close()
      except Exception:
          pass